The invention relates to high frequency woven electrical transmission cables used in high speed electronic equipment such as sophisticated telecommunication and computer systems wherein high speed switching circuitry is employed. In these applications the reliability and accuracy of the transmitted signals necessitates considerable attention and critical to achieving this is the requirement that the impedance of the cable be matched with the load of the input in order to transmit a representative accurate signal at the output.
Another source of signal error in this type cable is unwanted electrical noise picked up between adjacent conductors during the transmission of signals. In high speed logic circuits discrete signals of either a high or low value are normally transmitted for triggering the logic circuits. An error produced by unwanted electrical noise can produce false triggering of the logic circuits.
Isolating the signal wires from each other and controlling the impedance of the cable are problems to which considerable attention need be given in order to accurately transmit high frequency electrical signals in high technology electronic systems.
Various types of flat controlled impedance cables have been proposed. It has been proposed in U.S. Pat. No. 4,143,236 to weave a high frequency flat controlled impedance cable in such a manner that adjacent signals are isolated by pairs of ground wires with the location and configuration of the signal and ground wires fixed in the cable by means of the weave. In this manner, a very precisely controlled impedance cable can be provided. Other attempts to provide a controlled impedance cable which accurately transmits high frequency signals have included laminated cables such as disclosed in U.S. Pat. No. 3,634,782.
The use of an increasing number of pins in the terminal connectors in the electronic systems has required that more and more signal conductors be placed in the cable resulting in wider and wider flat cable structures. However, when the woven cable becomes too wide, it becomes difficult to route in the chassis of the equipment. In accordance with the present invention, up to twice as many conductors may be provided in the same width as the flat cables before. Where increased pins are not used, the cable may be made half the width as before without any increase in signal interference between adjacent conductors.
U.S. Pat. No. 3,815,054 discloses a low impedance, high frequency line wherein a plurality of insulated electrical wires are peripherally clustered in a ring about an idler center in a non-woven construction which is generally unrelated to the present invention.